Abstract
This study explored the genetic basis of growth traits in Middle Anatolian Merino lambs using multi-locus genome-wide association study (GWAS) analyses. Descriptive statistics indicated moderate heritability (h² = 0.363) for birth weight (BW) and (h² = 0.309) for weaning weight (WW), both statistically significant (p < 0.001). Strong genetic correlations were observed between WW and BW (rG = 0.922) and WW and Kleiber ratio (KR, rG = 0.896), implying that simultaneous improvements may be possible through targeted selection. Five multi-locus methods (mrMLM, FASTmrMLM, pLARmEB, FASTmrEMMA, and ISIS EM-BLASSO) were used to identify the polygenic basis of the traits. For BW and WW, 20 and 18 significant SNPs (LOD ≥ 5) were detected, respectively, with some SNPs co-detected by multiple methods. In contrast, only 10 significant SNPs were identified for KR, all exclusively by the ISIS EM-BLASSO approach. Pathway analyses within ± 100 Kb of associated SNPs revealed genes and pathways influencing these traits, which could be leveraged in future breeding programs for enhanced growth performance. The identified SNPs, particularly those associated with BW and WW traits, could facilitate genomic selection if validated in larger and more diverse populations.